Help with a 7104 Tektonix Scope

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#1 Post by **jdhurst** » Fri Nov 17, 2006 7:27 pm

I have a good Tektronix 7104 1Ghz scope. It works in most all respects except that a horizontal plugin in the B channel does not trigger internally. The A channel works fine, and I have eliminated the plugin (I have several).

I have a parts Tektronix 7104 that I picked up very cheap on eBay (under $100 working).

It occurs to me that the trigger selector board on the good scope may have a defect. I would like to try the trigger selector board from the parts scope, but it looks like a beggar to remove. It is attached to the backplane, and coax cables run through the trigger selector board into the backplane. It appears I would have to disconnect these cables at the other end, but some of them route up into the CRT area.

Has anyone here (of our thousands of members) ever removed the backplane in a 7000 series scope? If so, how, and how difficult?

Thanks, ... JD Hurst

#2 Post by **rkawakami** » Fri Nov 17, 2006 7:42 pm

Nice 'scope. We have two of them here but have never attempted to take them apart. We leave that to the calibration service. Do you have any of the service manuals for them? I'll check around here to see if I can locate one.

edit: Found an instruction manual dated "Revised FEB 1989". Section 4 is on Maintenance and appears to have some basic instructions on how to remove/replace the following:

Display Unit Kickstand
Power-supply Unit Removal
Cathode-ray Tube Removal
Cathode-ray Tube Replacement
Circuit Boards
Plug-in Interface Connectors
Delay Line Removal

I also found an eBay seller with a PDF of this manual (the part number of the manual matches what he has on the CD):

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 7503702847

#3 Post by **jdhurst** » Fri Nov 17, 2006 8:10 pm

I got the PDF manual with the Scope. I have some removal instructions, but actually doing this stuff is somewhat more difficult than described because of the complex routing of the cables. Also, when new, the CRT in that machine was near $10,000 to replace, and they don't recommend removal unless necessary. I have the Power supply out and the side boards removed, so I can clearly see the trigger selector. I know from the manual I have the correct board.

I can take the top (including CRT and delay lines) off my 7704A with several screws and one big plug (including coax disconnections). The top of a 7104 is nowhere near as easy to remove because of the multiple wiring connections.

Do you know who your calibration service is? If so, please consider posting the contact. I have a shipping container if I need it.

Thank you, ... JD Hurst

#4 Post by **rkawakami** » Fri Nov 17, 2006 8:22 pm

I don't have the name of the cal shop on hand at the moment. The lady who schedules the equipment for service has already gone home. It's somewhere close here to work since they come in to pickup and deliver the scopes or meters. I don't know if they also do any service or repairs. The 7104s have been very reliable (the plug-ins are another matter). If you can hold out until Monday I'll have the contact info for you.

#5 Post by **jdhurst** » Fri Nov 17, 2006 8:52 pm

I'm in no rush (this is a hobby). Thanks, Ray. If others have any experience or thoughts, please post. ... JD Hurst

#6 Post by **rkawakami** » Fri Nov 17, 2006 10:36 pm

I just had one of those DUH! moments... (must be due to my increa.. no! don't say it!)

I looked on the CAL STICKER on the scope. The company is PMI, Precision Measurements, Inc. and they are in Sunnyvale, CA. The Flash-heavy web site is at:

http://www.pmi-cal.com/

egibbs · #7 Post by **egibbs** » Mon Nov 20, 2006 7:10 am

Before you go to all that trouble JD, have you verified that the trigger selector SWITCH is working correctly?

Ed Gibbs

#8 Post by **jdhurst** » Mon Nov 20, 2006 10:25 am

Thanks Ed,
Yes, I replaced that switch (front panel selector) from the part scope. The original switch had a mechanical defect. Replacing it, however did not affect the trigger failure on the B channel.

I have the parts scope opened up on my bench, and getting the trigger selector board out is clearly a hassle, and then, I don't know if introducing it to the good scope will cause a calibration hassle.

Certainly I replace the vertical amplifier board because of a connector defect on the original board, but that caused all kinds of grief. I restored the original board and all is well (though I have a connector defect on that board).

Thank you, ... JD Hurst

Help with a 7104 Tektonix Scope

Help with a 7104 Tektonix Scope

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